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VRM technology past, present and future: Carsten Schoessow, Gebr Pfeiffer (Germany)

Filmed at Cemtech MEA 2015, 8-11 February, Grand Hyatt Dubai, UAE

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So I would like to present the Gebr Pfeiffer my company, and as we have the name of the presentation, I will start with the past because it was our history, and our history is very long because we celebrated last year our 150th birthday together with our clients. I want to show you some highlights which is at the beginning, the start 151 years ago, and we have some highlights here as the first vertical roller mill for cement grinding.

Actually, it's still in operation in Germany and we have established some subsidiaries in India and United States and later on we come to our new mill type which I will also present in this presentation. So what are are highlights around Gebr Pfeiffer? So we have vertical roller mills for grinding of cement raw material, coal and clinker, slag, whatever. In coal grinding, we also have a lot of references in the coal mills for power plants, where we have a licensing agrement with Babcock & Wilcox, United States, and I don't know the actual name I think Babcock Hitachi in Germany.

Another area is the grinding and calsigning[sp?] of tripson[sp?], where we're supplying our MPS mills for the production of there wall bolts. Latest points I will also show later more in detail is the last plant Wilson MVR Mill, which went onto operation in Port Kembla Australia. This is a grinding station, and the owners of this plant is a 50%-50% share between Houston and Hydrotech cement. If we now come to the grinding technologies, we have in Gebr Pfeiffer, we have first of all the well known MPS mill, which we are using for grinding of raw material, coal and clinker and for higher capacities, we have now developed the new MVR mill.

First of all I want to show you something special of Gebr Pfeiffer because we have our own workshop. So since the beginning, we are producing the key parts of our mills ourself. Still today, we are, for example, special parts like grinding rollers are completely assembled in our workshop in Germany, and then sent to the final destination.

Here you see some pictures as the huge grinding rollers of the MVR mills, rocker arms, and we even have a small foundry to cast some parts of the ware parts of the mill. If we now go on to the MPS mill, which I showed you before, we have now sold more that 2, 000 MPS mills to the industry. If we look on our references within the last 20 years, you see here, nearly 200 MPS mills for the grinding of cement raw material, more than 100 for coal grinding and around 60 for the grinding of clinker and slag.

Here I show you of the MPS mills always the biggest sizes, which have been supplied, and we have an MPS 5600 mills, it's a 5.6 table diameter, and the throughput for this plant in India is 650 tonnes per hour. In coal grinding, we have supplied the biggest coal mill in the world. It's in Indonesia in bio-cement for the grinding of [xx] coal in Indonesia with dry size of 1,300 kilowatt.

and the biggest MPS mill for the grinding of clinker and slag, is the MPS 5600. So, this is again a 5.6 meter table diameter, and this mill is also operation in India. The problem we face at a certain time at MPS mill was that we have a fix number of steel rollers, which means all the kilns are getting bigger here at Emirates, we also have already ten thousand ton per day kilns in Saudi Arabia too, and that means you need capacities for the mills to grind 8-900 tonnes per hour of cement raw material, and you need cement mills, which are able to grind three hundred or even more than three hundred tonnes per hour, and in this case, we are coming to a certain limit with our MPS mill, because we have to increase the diameter of our grinding rollers, and at the end, we came to a dimension, where one grind, the weight of one grinding roller was more than 80 tonnes, and that's why, we decided to develop a new mill for the higher capacities, and the name for this mill is MVR mill. This is the picture of this

 mill. So, we're getting the hot gases here like we know it also from the MPS mill. Into the mill, we feed the material from the top and the ground product is leaving the mill though the classifier to the cyclones or back filter depending on the application. Then the big change compared to CMPS mill is, that we now have single guided holders, with the rocker arm, and so we increased also the number of rollers, smaller mills have four grinding rollers, and bigger mills have six grinding rollers.

So we are coming down to weight of the roller, where it is possible to handle it for maintenance. And to give a summary of the advantages, so we start with what we call the active redundancy. So this seems to be a nice new word, but it means that when we talked about the big capacities that we have in future, for example cement mills grinding 4-5-600 tonnes per hour, so the reliability of these mills is very important, and we have developed a system with this mill where we have also created a new drive system, which is called the multi drive.

The Multi drive, which I will explain later in detail is a reaction on the big amount of gearbox failures which happened approximately six, seven years ago, where planetary gearboxes was broken inland shift and so on, where stopping vertical roller mills for long time, and we have developed a complete new drive, where let's say this traditional gearbox is not necessary anymore, and due to that, we have a system where we can, and these are the two major problems you can have with your roller mill, would mean you have a problem with the grinding roller whichyou have not getting seeding into the roller, you have a problem with the bearing obviously lubrication system.

An active redundancy means in our case, that you can swing out one roller, and you keep the mill alive let's say, and you're running the mill with the remaning three or five rollers. So in a six rollers mill, it means if you have a problem with one roller, you bring one roller out, and then you start the operation again, and you run the mill appoxiatemately with 85% of the original capacity, and just to give you one information about that, if you would have two cement mills without the system, and you have a problem with the roller, here you have to turn down one complete cement mill, so you the remaining capacity is only 50%.

So in this example we're showing that with one mill, with one huge mill for example one mill and one kiln, the redundancy is even higher as if you have two mills because we're only losing 15% of the throughput if we have a problem with one roller. And the same is with the gear box. If one gearbox of our multiple drives will fail, we can operate with the rest of the remaining drives.

So this is the only existing rear multi-drive, where it doesn't matter what happens you always can keep the mill in operation, but only the server reduced capacity. Next point is, hydraulic system for operation and maintenance. We found, we looked on all the vertical roller mills ,and we found it very complicated that you always need devices, swing out devices, maintenance devices whatever, so we have developed a system now where we use the operation hydraulics, and where we generate the grinding pressure. This cylinder, you can also use for slinging[sp?] out the roller, so you don't need additional hydraulic cylinders, additional devices, so you can sling out the whole more rollers at the same time for example, and you do not need these maintenance devices.

Parallel grinding [xx]. Also we have the special movement our roller, and I'll show you all this in detail after that is moving onto the table, and we always maintain a parallel grinding gap between the roller and the table. The modular drive system. With this multi drive we have modules, modules means the motor and the gearbox together, and we can for a new project, we can arrange proposals to you that the whole mill and the cement mills for example they have the same multiple drive modules, so that motor and gearbox is interchangeable between the whole mill, and the cement mill, or if you have more than one kiln, even internationally you can interchange this parts between different mill sizes.

Our ware parts are symmetric. It means all the rollers in every vertical roller mills, they have a certain uneven wear so the wear outside of the table is always higher than the wear inside, and our tyres, you can even turn around and use them in this position also. We have thought a lot about how to locate six grinding rollers around the table.

The problem is, if you put six rollers around the table will have no space anymore for the hot gas inlet and for doing maintenance on the gearbox, and our idea and this is also unique, our solution is to put two rollers on one pedestal. With this we get a lot of open space where we can do maintenance on the drive, and also we have enough area to get the hot gases into the mill.

This is not. In detail what I told you, for maintenance you just open the door, and you swing out the roller. This is same hydraulics cylinder what you are using for the generation of the grinding pressure. And here you see again what the parallel grinding gets, so we are moving the roller up and down, parallel to the table, and that's we always maintain the parallel grinding gap.

Okay again, a picture showing how to do the maintenance on the roller. And now we come to the multi drive little bit more on detail. So the table, so if you look on the normal vertical roller mill, we just first of all delete the gear box. We take it away. We move the table down, and we put the table on a so called table support.

Our table support is consisting of two Mitchells or thrust-bearings, but you already know because you have this on top or your traditional gearbox also. But what we have, we have both, we are taking the axial as well as radial forces. And around this table support, we put the gasket here, and we drive here, lets say this way the table is supported on this support, and all the grinding forces are going through the table into the foundation, and our drive modules the only thing they have to do is to [xx] to rotate the table.

So the forces of grinding, the differences in the grinding bet high, whatever happens to this machine, the cause of vibrations, is not going into the gear box, it's just going through the table support into the foundation. You can, let's say compare this to the drive of the kiln. This is I think a good example and our drive system is very similar.

Again you see here is the picture of some [xx] drive and also here the peak, free area of access which we have because we put two grinding rollers onto one pedestal. This is now one the same picture again showing the situation with the six roller mill. Now, and the active redundancy is so here again. So we have let's say taken one roller out of operation, and that's also very important difference. All other system on the market also called multiple drives or whatever, they do not allow that you swing out only one roller. You always have to swing out also opposite roller, because otherwise you may get unevenly forces on your thrust bearing, what you have in this gear box.

Only the Gebr Pfeiffer multi drive offers the possibility to swing out one roller only. This is very important because we discussed before about redundancy so you buy one big mill, and then if you swing on one roller, you lose 15% of the throughput, if you have to swing out two, even the second one is not still okay. and you lose 30% of the throughput. So this is again a disadvantage compared to this system, and we have to when we designed this mill, our main aim was to get the highest possible redundancy because we think this is the next generation of mills, which is working with, I don't know, 10, 000, 12, 000 kilo per drive because the economy scale is always there.

You are looking on bigger kiln sizes to save investment cost and the same as these grinding equipment. If you would install one big cement mill instead of two, then you save, let's say 25% of your investment cost, because of the economy of scale. This shows now how to do maintenance. So with an overhead crane, we can take off, or with the mobile train then mill can stand also outside. We can take off the tyre, and here we also take off the, take out the liners on the grinding table, if they have to be replaced.

The material of these tyres, there is a big, we have many possibilities to use, for example high com parts also ceremic, so if you have few grinding select or if you have wear on your elements, we can also use the new developed [xx] cast or [xx] or whatever you call materials for these liners. So this is now already our [xx] so, few year after introducing, I'm not sure if you can see that I will go a little bit slowly. This is our references for the MVR mill.

So we have already sold 20, and I think this is not bad and including in the 20 like it is very often most of mills, we have sold in India. So you see here big lines are Sree cement, Emami cement. They have already, everybody like six, seven MVR mills for grinding of cement raw materials as well as for the grinding of clinker.

Another big customer is Lafarge. So for the modernization projects [xx] and so on in united States, they have also bought the MVR mill, and we have a big order here from Lafarge which is performed via CBMI for Algeria. So in Algeria, they're building a new line, and they will have a raw mill as an MVR mill, and they will also will install the second biggest cement mill in the world with some 9900 kilo per drive, multi-drive.

This is another overview where we are today in the world where our projects, so I told you a little bit already Port Kembla, Australia [xx] operation. We have here, Shree cement, four cement mills, 6700 kilowatts, traditional gear box drive. We have another Shree cement in [xx], [xx] I told you extra the two Lafarge projects in United states.

These are the projects we have, and we see here but also, I'll show you in some minutes more details. This is the biggest cement mill in the world, 11500 kilowatt drive. Unfortunately, not in operation. There is a big delay in the erection, and we are very much pushing, and we are interested that. This mill is going to the operation showing our clients what such a mill can produce, and I'll show you later the guaranteed figure of that mill.

But before I do this I give you some more details about the Port Kembla plant. So in Port Kembla, this is a grinding station, and this project was done together with our friends from Cement Guy, Cement Guy was the EPC contractor, and Gebr Pfeiffer was the sub supplier for equipment. The guarantee has been 280 tonnes per hour of the same, one and 190 tonnes per hour granulated [xx]. Here you see the different fineness, so where is it?

It's in the house of Sydney, in a harbor called Port Kemblar, very close to a new plant, and here they have some unloading facilities for the unloading of clinker and slag. I go further, and we've supplied the MVR 6000 C6 that means it's a six meter table diameter, six rollers and the C means, this is a clinker or even slag mill. Six rollers, diameter of each roller, 2.1 meter and the weight of the complete roller group is approximately 50 tones per hour, 50 tonnes each of power..

This is a flow sheet, this is a typical flow sheet from vertical roller mills for grinding clinker or slag, this is the recheck system of mill, a back filter, fan and hot-gas innovator, which you mainly use when you dry the slag. In this plant, we have to gather this wholesome[sp?] developed other thing which is unique. This is a separate grinding system for gypsum. There are two reasons for that.

They are, to dehydrate the gypsum, you need a lot higher temperature, and to let's say grind and dry the OPC. We see separate grinding of gypsum, we can work at higher temperatures, we can control the degree of the hydration, and this helps you to control for example the setting times of the cement you're producing, and Australia is one of the most difficult countries with the highest regulations, and therefore, we have the system. Also I have some clients talking about clogging in the cement silos where cement silo outlets are blocked because of problem with the gypsum, and this is the solution for that.

So we have added here, a [xx] mill. [xx] not MPS, because of the small throughput. This is separate hot gas generator, and we're feeding the natural gypsum. We're producing necessary heat here in the hot gas generator, and then we're conveying this ground gypsum into the classifier because it's already fine enough. And here you see why we do that. If we run the mill with 70 degrees grinding OPC so we have a zero percent degree of dehydration of the gypsum. If we want to get a partial calsigning in the mill then we have to increase the outer temperature of the mill, but we need a huge amount of heat, because we're, let me say the easy way, we have to heat up only 5% gypsum, but here in this case we're heating up 95% clinker, which is not necessary, and this is separate grinding of gypsum, so with lower amounts of energy, we can go upto 93% degree of dehydration of the gypsum.

This is also a system, which is I think the only project, where Port Kembla is using this separate gypsum grind. And this is the picture here showing the [xx] mill, which we have installed in the plant. Some pictures from the site. So this is the harbor area. Here we have in this case steel silos, not concrete silo. Australia is the country with the highest erection cost in the world, so the idea of our EPC contractor was to as much as possible pre fabricate everthing in Spain and ship it to Australia.

If you put in youtube Port Kembla or Cement Grind, you'll see a lot of very interesting movies how these parts have been shipped to Australia. This is the mill housing, it here's the erection site we the three pedestals for the six rollers. You get mill housing and classifier. Table support for the multi drive, and now we've already installed six climbing rollers, and as I told you before also we're not using any, how can I say? master support, all of our grinding rollers all are grinding the same way, and here you see this twin support of the roller itself with the lubrication and seeding supply to the rollers.

Now, the mill is erected but the classifier still missing and then we put the classifier on, and this is a picture of the whole grinding station that is now in operation for several months, and its a nice reference for anybody, who wants to go to Australia. Let us know, and we will try to get a permit from person [xx] visited. Okay and now I come to the biggest vertical roller mill in the world. This was placed already more than three years ago, but unfortunately there is a big delay in the project.

Also here, this is FCB kiln, and also cement guy is involved, and this would be, the biggest cement mill before had a drive size of 6-7000 Kilowatt. You see this is nearly double of that size, and unfortunately due to delay in civil works and direction in Brazil, this, mill is still not in operation.

But, believe me, if we get the first designs, we will inform you, our clients immediately, because this is of course a big advantage for us to show that these mills are also in operation. Our guarantee figure for this mill, doesn't look so high as expected, but you have to see, will we have here like 450 tonnes, this is a 4300 [xx] fineness and we have 34% of slag.

This is of course more difficult to grind then normal clinker. OIf you would use this for producing limestone cement, is many customers like [xx], for example they are mixing 25%, 30% of limestone into the clinker, you would easily produce like 600 tonnes per hour with this one machine and the reason that the Houston decided for that is what I told you before, that we can swing out one roller in case of problems with the roller, and then we can also work with for example, with five drives if one gear box fails. There's also another advantage of these modules because this gear boxes are very small. In case of any problem, this gear box can be send via air freight. So try this with a normal gearbox. A normal gearbox 6500 kilowatt, the weight is more than 100 tonnes, so you need a special transport. But this small gearbox is, you can put it into a plane and fly it to any area where you need it. But we've also, I mean this conference also not only for Saudi Arabia, Emirates, but also for Africa as not so many people from Africa here, but we have also, and I showed you this before, sold the biggest vertical roller mill in Africa and this is Folafas, Biska, in Algeria and we will now in some weeks start delivery, and hopefully in one year, we will start the operation in ALgeria, and this is very similar to the mill we have in Barroso, Brazil, but we have one drive less, so instead of six multi drives, we have five, and that's why the drive size is a little bit smaller.

This is a picture of this, how can I say? Monster mill. You see in some weeks hopefully we can you have three pictures, but it looks like also the smaller mills, but as I told you before, you will save 25% of investment cost if you build one grinding plant instead of two, and also here in Saudi Arabia, we have now a lot of projects for huge kilns, and we're ready to promote this solution, this one mill solution for grinding mill.

So very fast now, we jump to the multi drive because also yesterday there was another presentation of the another multiple drive, and here you see, this is our tables apart, and we have the multiple drives around that, and this is the picture from JP in Balaji in India. Here you can see, I think, very good, the table support, the gas gear and then the single small gearboxes orl small drives, which are only rotating [xx] which is very important, we have multiple gear boxes, multiple drives. We do not have one gear box, some number of motors.

This is the answer on gear box failures and the grinding forces are completely going bypassing, let's say in the gearboxes, these gearboxes are the only thing we have to do to rotate the table. There we have also modular systems with different modules, and you see detail we have here the small gearbox, the motar and also we have a frequency converter, which is to synchronize the separate the multi drives, but we are working very hard on a solution to delete the frequency converters because this is a expensive solution for home use for example we don't need these raw mills, we don't need different table speeds or for cement mills, where we're only producing one or two similar qualities. Also in the near future deletes the frequency converter, and reduce the investment cost on this life's solution.

This is now very important because is the reason you see here. This is the axial thrust bearing. This you have already on your normal gearbox, but with this only if you have a problem with the roller, you have to swing out also the opposite roller because otherwise you get uneven forces in this thrust bearing. And our solution is this radial thrust bearing. This is taking the loads if we swing out only one roller, and that's why it is possible. And you see here the gas, the gas gear box which is, let's say, rotating than the table by moving the gas gear.

This is a construction going of the same multi drive again, and there's also one other advantage. If you go to Port Kembla, we have a vibration speed at the mill, 0.5 millimeters per second. So it's 10% of what you can have in other vertical roller mills. Why is that? Because we delete the gear box, so whole mill is coming 2-3 meters down, less in height. The center of gravity is 2 to 3 meters more down compared to other vertical roller mills [xx] conventional drive. So this also reduces the vibration.

So with that I thank you very much. Some people, more people came in, and I hope I showed the advantages of vertical roller mills of Gebr Pfeiffer. Thank you very much!

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